diff --git a/include/xemmai/class.h b/include/xemmai/class.h
index 9baa0959..57ccbd22 100644
--- a/include/xemmai/class.h
+++ b/include/xemmai/class.h
@@ -15,7 +15,7 @@ struct t_type_of<t_type> : t_uninstantiatable<t_bears<t_type>>
 		f_finalize = f_do_scan;
 		v_get = static_cast<t_pvalue (t_type::*)(t_object*, t_object*, size_t&)>(&t_type_of::f_do_get);
 		f_string = f_hash = f_not_supported0;
-		f_get_at = f_set_at = f_plus = f_minus = f_not = f_complement = f_multiply = f_divide = f_modulus = f_subtract = f_left_shift = f_right_shift = f_less = f_less_equal = f_greater = f_greater_equal = f_equals = f_not_equals = f_and = f_xor = f_or = f_not_supported1;
+		f_get_at = f_set_at = f_plus = f_minus = f_complement = f_multiply = f_divide = f_modulus = f_subtract = f_left_shift = f_right_shift = f_less = f_less_equal = f_greater = f_greater_equal = f_equals = f_not_equals = f_and = f_xor = f_or = f_not_supported1;
 	}
 	static void f_do_scan(t_object* a_this, t_scan a_scan);
 	XEMMAI__PORTABLE__EXPORT t_pvalue f_do_get(t_object* a_this, t_object* a_key, size_t& a_index);
diff --git a/include/xemmai/fiber.h b/include/xemmai/fiber.h
index b3ab4ee2..b79ed42e 100644
--- a/include/xemmai/fiber.h
+++ b/include/xemmai/fiber.h
@@ -306,21 +306,6 @@ inline t_pvalue t_value<T_tag>::f_##a_name() const\
 XEMMAI__VALUE__UNARY_ARITHMETIC(plus, )
 XEMMAI__VALUE__UNARY_ARITHMETIC(minus, -)
 
-template<typename T_tag>
-inline t_pvalue t_value<T_tag>::f_not() const
-{
-	auto p = static_cast<t_object*>(*this);
-	switch (reinterpret_cast<uintptr_t>(p)) {
-	case e_tag__NULL:
-		return true;
-	case e_tag__INTEGER:
-	case e_tag__FLOAT:
-		return false;
-	default:
-		XEMMAI__VALUE__UNARY(f_not)
-	}
-}
-
 template<typename T_tag>
 inline t_pvalue t_value<T_tag>::f_complement() const
 {
diff --git a/include/xemmai/global.h b/include/xemmai/global.h
index abae019b..e2b007ba 100644
--- a/include/xemmai/global.h
+++ b/include/xemmai/global.h
@@ -59,7 +59,6 @@ class t_global : public t_library
 	t_slot v_symbol_set_at;
 	t_slot v_symbol_plus;
 	t_slot v_symbol_minus;
-	t_slot v_symbol_not;
 	t_slot v_symbol_complement;
 	t_slot v_symbol_multiply;
 	t_slot v_symbol_divide;
@@ -121,10 +120,6 @@ class t_global : public t_library
 	{
 		return v_symbol_minus;
 	}
-	t_object* f_symbol_not() const
-	{
-		return v_symbol_not;
-	}
 	t_object* f_symbol_complement() const
 	{
 		return v_symbol_complement;
@@ -535,7 +530,7 @@ intptr_t t_fiber::f_main(T_main a_main)
 			} else {
 				std::fprintf(stderr, "caught: <unprintable>\n");
 			}
-			if (f_is<t_throwable>(thrown)) thrown->f_invoke_class(/*dump*/26);
+			if (f_is<t_throwable>(thrown)) thrown->f_invoke_class(/*dump*/25);
 		}
 	} catch (...) {
 		std::fprintf(stderr, "caught: <unexpected>\n");
diff --git a/include/xemmai/type.h b/include/xemmai/type.h
index ece3d4a7..aa09c1e1 100644
--- a/include/xemmai/type.h
+++ b/include/xemmai/type.h
@@ -200,10 +200,6 @@ struct t_type_of<t_object>
 	{
 		return a_self.f_tag();
 	}
-	static bool f__not(const t_pvalue& a_self)
-	{
-		return false;
-	}
 	static bool f__equals(const t_pvalue& a_self, const t_pvalue& a_other)
 	{
 		return a_self == a_other;
@@ -325,8 +321,6 @@ struct t_type_of<t_object>
 	size_t (*f_plus)(t_object*, t_pvalue*) = f_do_plus;
 	XEMMAI__PORTABLE__EXPORT static size_t f_do_minus(t_object* a_this, t_pvalue* a_stack);
 	size_t (*f_minus)(t_object*, t_pvalue*) = f_do_minus;
-	XEMMAI__PORTABLE__EXPORT static size_t f_do_not(t_object* a_this, t_pvalue* a_stack);
-	size_t (*f_not)(t_object*, t_pvalue*) = f_do_not;
 	XEMMAI__PORTABLE__EXPORT static size_t f_do_complement(t_object* a_this, t_pvalue* a_stack);
 	size_t (*f_complement)(t_object*, t_pvalue*) = f_do_complement;
 	XEMMAI__PORTABLE__EXPORT static size_t f_do_multiply(t_object* a_this, t_pvalue* a_stack);
@@ -374,7 +368,6 @@ struct t_type_of<t_object>
 		if (T::f_do_set_at != U::f_do_set_at) f_set_at = T::f_do_set_at;
 		if (T::f_do_plus != U::f_do_plus) f_plus = T::f_do_plus;
 		if (T::f_do_minus != U::f_do_minus) f_minus = T::f_do_minus;
-		if (T::f_do_not != U::f_do_not) f_not = T::f_do_not;
 		if (T::f_do_complement != U::f_do_complement) f_complement = T::f_do_complement;
 		if (T::f_do_multiply != U::f_do_multiply) f_multiply = T::f_do_multiply;
 		if (T::f_do_divide != U::f_do_divide) f_divide = T::f_do_divide;
@@ -498,7 +491,6 @@ struct t_derived : T
 		this->f_set_at = t_type::f_do_set_at;
 		this->f_plus = t_type::f_do_plus;
 		this->f_minus = t_type::f_do_minus;
-		this->f_not = t_type::f_do_not;
 		this->f_complement = t_type::f_do_complement;
 		this->f_multiply = t_type::f_do_multiply;
 		this->f_divide = t_type::f_do_divide;
diff --git a/include/xemmai/value.h b/include/xemmai/value.h
index bbab3fc8..e6a3df9e 100644
--- a/include/xemmai/value.h
+++ b/include/xemmai/value.h
@@ -351,7 +351,6 @@ class t_value : public T_tag
 	t_value<t_pointer> f_set_at(const t_value<t_pointer>& a_index, const t_value<t_pointer>& a_value) const;
 	t_value<t_pointer> f_plus() const;
 	t_value<t_pointer> f_minus() const;
-	t_value<t_pointer> f_not() const;
 	t_value<t_pointer> f_complement() const;
 	t_value<t_pointer> f_multiply(const t_value<t_pointer>& a_value) const;
 	t_value<t_pointer> f_divide(const t_value<t_pointer>& a_value) const;
diff --git a/src/code_operator.h b/src/code_operator.h
index 9b772f83..d134884b 100644
--- a/src/code_operator.h
+++ b/src/code_operator.h
@@ -37,17 +37,7 @@
 		XEMMAI__CODE__UNARY_ARITHMETIC(PLUS, , f_plus)
 		XEMMAI__CODE__UNARY_ARITHMETIC(MINUS, -, f_minus)
 		XEMMAI__CODE__CASE_BEGIN(NOT)
-				switch (a0.f_tag()) {
-				case e_tag__NULL:
-					XEMMAI__CODE__PRIMITIVE_CALL(true)
-					break;
-				case e_tag__INTEGER:
-				case e_tag__FLOAT:
-					XEMMAI__CODE__PRIMITIVE_CALL(false)
-					break;
-				default:
-					XEMMAI__CODE__OBJECT_CALL(f_not)
-				}
+				XEMMAI__CODE__PRIMITIVE_CALL(!a0)
 		XEMMAI__CODE__CASE_END
 		XEMMAI__CODE__CASE_BEGIN(COMPLEMENT)
 				if (a0.f_tag() == e_tag__INTEGER) {
diff --git a/src/global.cc b/src/global.cc
index 33e2c7e7..78640bb2 100644
--- a/src/global.cc
+++ b/src/global.cc
@@ -42,7 +42,6 @@ void t_global::f_scan(t_scan a_scan)
 	a_scan(v_symbol_set_at);
 	a_scan(v_symbol_plus);
 	a_scan(v_symbol_minus);
-	a_scan(v_symbol_not);
 	a_scan(v_symbol_complement);
 	a_scan(v_symbol_multiply);
 	a_scan(v_symbol_divide);
@@ -79,7 +78,6 @@ std::vector<std::pair<t_root, t_rvalue>> t_global::f_define()
 	v_symbol_set_at = t_symbol::f_instantiate(L"__set_at"sv);
 	v_symbol_plus = t_symbol::f_instantiate(L"__plus"sv);
 	v_symbol_minus = t_symbol::f_instantiate(L"__minus"sv);
-	v_symbol_not = t_symbol::f_instantiate(L"__not"sv);
 	v_symbol_complement = t_symbol::f_instantiate(L"__complement"sv);
 	v_symbol_multiply = t_symbol::f_instantiate(L"__multiply"sv);
 	v_symbol_divide = t_symbol::f_instantiate(L"__divide"sv);
diff --git a/src/type.cc b/src/type.cc
index d624d4dd..e13dc805 100644
--- a/src/type.cc
+++ b/src/type.cc
@@ -32,7 +32,6 @@ void t_type::f_define()
 		(f_global()->f_symbol_set_at(), f_not_supported)
 		(f_global()->f_symbol_plus(), f_not_supported)
 		(f_global()->f_symbol_minus(), f_not_supported)
-		(f_global()->f_symbol_not(), t_member<bool(*)(const t_pvalue&), f__not>())
 		(f_global()->f_symbol_complement(), f_not_supported)
 		(f_global()->f_symbol_multiply(), f_not_supported)
 		(f_global()->f_symbol_divide(), f_not_supported)
@@ -242,24 +241,23 @@ XEMMAI__TYPE__METHOD(get_at, 4, 1)
 XEMMAI__TYPE__METHOD(set_at, 5, 2)
 XEMMAI__TYPE__METHOD(plus, 6, 0)
 XEMMAI__TYPE__METHOD(minus, 7, 0)
-XEMMAI__TYPE__METHOD(not, 8, 0)
-XEMMAI__TYPE__METHOD(complement, 9, 0)
-XEMMAI__TYPE__METHOD(multiply, 10, 1)
-XEMMAI__TYPE__METHOD(divide, 11, 1)
-XEMMAI__TYPE__METHOD(modulus, 12, 1)
-XEMMAI__TYPE__METHOD(add, 13, 1)
-XEMMAI__TYPE__METHOD(subtract, 14, 1)
-XEMMAI__TYPE__METHOD(left_shift, 15, 1)
-XEMMAI__TYPE__METHOD(right_shift, 16, 1)
-XEMMAI__TYPE__METHOD(less, 17, 1)
-XEMMAI__TYPE__METHOD(less_equal, 18, 1)
-XEMMAI__TYPE__METHOD(greater, 19, 1)
-XEMMAI__TYPE__METHOD(greater_equal, 20, 1)
-XEMMAI__TYPE__METHOD(equals, 21, 1)
-XEMMAI__TYPE__METHOD(not_equals, 22, 1)
-XEMMAI__TYPE__METHOD(and, 23, 1)
-XEMMAI__TYPE__METHOD(xor, 24, 1)
-XEMMAI__TYPE__METHOD(or, 25, 1)
+XEMMAI__TYPE__METHOD(complement, 8, 0)
+XEMMAI__TYPE__METHOD(multiply, 9, 1)
+XEMMAI__TYPE__METHOD(divide, 10, 1)
+XEMMAI__TYPE__METHOD(modulus, 11, 1)
+XEMMAI__TYPE__METHOD(add, 12, 1)
+XEMMAI__TYPE__METHOD(subtract, 13, 1)
+XEMMAI__TYPE__METHOD(left_shift, 14, 1)
+XEMMAI__TYPE__METHOD(right_shift, 15, 1)
+XEMMAI__TYPE__METHOD(less, 16, 1)
+XEMMAI__TYPE__METHOD(less_equal, 17, 1)
+XEMMAI__TYPE__METHOD(greater, 18, 1)
+XEMMAI__TYPE__METHOD(greater_equal, 19, 1)
+XEMMAI__TYPE__METHOD(equals, 20, 1)
+XEMMAI__TYPE__METHOD(not_equals, 21, 1)
+XEMMAI__TYPE__METHOD(and, 22, 1)
+XEMMAI__TYPE__METHOD(xor, 23, 1)
+XEMMAI__TYPE__METHOD(or, 24, 1)
 
 void f_throw_type_error [[noreturn]] (const std::type_info& a_type, const wchar_t* a_name)
 {
diff --git a/test/operators.xm b/test/operators.xm
index c1ea3493..b3fe5f05 100644
--- a/test/operators.xm
+++ b/test/operators.xm
@@ -6,7 +6,6 @@ Foo = Object + @
 	$__set_at = @(x, y) "a[" + x + "] = " + y
 	$__plus = @ "+a"
 	$__minus = @ "-a"
-	$__not = @ "!a"
 	$__complement = @ "~a"
 	$__multiply = @(x) "a * " + x
 	$__divide = @(x) "a / " + x
@@ -31,7 +30,6 @@ assert(a["x"] == "a[x]"
 assert((a["x"] = "y") == "a[x] = y"
 assert(+a == "+a"
 assert(-a == "-a"
-assert(!a == "!a"
 assert(~a == "~a"
 assert(a * "x" == "a * x"
 assert(a / "x" == "a / x"